Method and Apparatus for a Seal Ring Structure

ABSTRACT

A wafer seal ring may be formed on a first and/or a second wafer. One or both of the first and/or second wafers may have one or more dies formed thereon. The wafer seal ring may be formed to surround the dies of a corresponding wafer. One or more die seal rings may be formed around the one or more dies. The wafer seal ring may be formed to a height that may be approximately equal to a height of one or more die seal rings formed on the first and/or second wafer. The wafer seal ring may be formed to provide for eutectic or fusion bonding processes. The first and second wafers may be bonded together to form a seal ring structure between the first and second wafers. The seal ring structure may provide a hermetic seal between the first and second wafers.

PRIORITY CLAIM AND CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 13/759,549, entitled “Method and Apparatus for a Seal RingStructure,” filed on Feb. 5, 2013, which application is incorporated byreference herein in its entirety. The present application is related toco-pending U.S. patent application Ser. No. 13/759,201, entitled “Methodand Apparatus for a Wafer Seal Ring,” filed on Feb. 5, 2013, commonlyassigned to the assignee of the present application, which applicationis incorporated by reference herein in its entirety.

BACKGROUND

In a semiconductor manufacturing process, integrated circuits (alsoreferred to as “dies”) are fabricated in a die area on a semiconductorwafer. The semiconductor wafer goes through many processing steps beforethe dies are separated by cutting the semiconductor wafer. Theprocessing steps can include lithography, etching, doping, grinding,blade cutting, die-sawing and/or depositing different materials. Theprocessing steps can include wet and dry processing steps. Semiconductorwafers and/or separated dies can be stacked or bonded on top of eachother to form a three-dimensional (“3D”) IC. For example, asemiconductor wafer with micro electrical devices formed within can bebonded to another semiconductor wafer with micro electrical-mechanicalsystem (“MEMS”) devices formed within the wafer. After bonding, thewafers are cut or separated into bonded dies, which consists of devicesfrom both wafers. In another example, a semiconductor wafer with MEMSdevices formed within can also be bonded with another capping wafer thathas cavities or recesses formed within. After bonding, the wafers arecut or separated into bonded dies, which consist of MEMS devices and acorresponding cap. During processing and bonding procedures,contaminants, chemicals, or residue may penetrate the die area and mayadversely affect production yield of dies formed therein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present embodiments, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a plan view of a wafer seal ring according to anembodiment;

FIG. 2 illustrates a plan view of another wafer seal ring according toanother embodiment;

FIGS. 3A-3C illustrate cross-sectional views of intermediate stages offorming a wafer seal ring in accordance with an embodiment;

FIGS. 4A-4D illustrate cross-sectional views of intermediate stages forforming a wafer seal ring in accordance with various embodiments; and

FIGS. 5A-5D illustrate cross-sectional views of intermediate stages forforming a wafer seal ring in accordance with various embodiments.

DETAILED DESCRIPTION

The making and using of the embodiments of the present disclosure arediscussed in detail below. It should be appreciated, however, that thepresent disclosure provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the disclosed subject matter, and do not limit the scope of thedifferent embodiments.

Before addressing illustrative embodiments of the present disclosure indetail, various embodiments and advantageous features thereof will bediscussed generally. For example, in some embodiments wafer levelbonding may be performed wherein one or more of the wafers may be aprocessed wafer having dies formed thereon, wherein each die may includeelectrical devices and/or circuits. It should be noted that althoughembodiments discussed herein are described in the context of bondingprocessed wafers, other embodiments may bond processed or unprocessedwafers, carrier wafers, interposers, other types of substrates, or thelike.

In an embodiment, die seal rings may be formed around one or more of thedies on a wafer, thereby providing die-level protection for the dieswithin each die seal ring of the bonded wafers. Wafers having diesformed thereon may also include test pads that may be used to connect toand/or test the functionality of electrical devices that may be formedwithin the dies. The test pads may be outside the die bonding pads orring encircling the die(s), such as within the scribe lines of thewafer.

After bonding a pair of wafers, the bonded structure may be furtherprocessed, for example, to thin the wafers, form electrical connections,bonding additional wafers and/or substrates, or the like. Previoustechniques for creating a seal between wafers utilized clamping alongthe edges of a pair of bonded wafer to seal the wafers. This previoustechnique resulted in an irregularly shaped, singular seal ringsurrounding the dies. Post-bonding processing may expose the test padsand the die bonding pads to chemicals or processing residue that maycorrode or damage the pads. Advantages of the embodiments describedherein include dual ring die protection utilizing both die seal ringsand wafer seal rings, as well as providing protection for the diebonding pads, die seal rings, the test pads and or the like using thewafer seal rings and/or seal ring structures.

Referring now to FIG. 1, there is illustrated a wafer 100 having a waferseal ring 110 according to an embodiment. As illustrated in FIG. 1, thewafer seal ring 110 may be formed on a wafer 100 such that the waferseal ring 110 surrounds one or more dies 120. The wafer seal ring 110may be formed between the dies 120 and an exterior edge of the wafer100. FIG. 1 further shows die seal rings 122 encircling each of the oneor more dies 120. Each of the dies 120 may be electrically coupled toone or more conductive test pads 124 that may provide electricalconnections to test and/or verify functionality of electrical devices(not shown) that may be formed in the dies 120. FIG. 1 illustrates thatthe test pads 124 are positioned outside of the die seal rings 122 forillustrative purposes, and in other embodiments, the test pads 124 maybe positioned within, outside, or both within and outside of the dieseal rings 122.

The wafer seal ring 110, as shown in FIG. 1, may be formed having acircular shape outlining a perimeter surrounding the dies 120. The waferseal ring 110 may have an approximately uniform width W. The width W ofthe wafer seal ring 110 may be sized based on area of the wafer 100 notoccupied by the dies 120, design guidelines and/or limitations of theequipment used to form the wafer seal ring 110. In an illustrativeexample that is not meant to limit the embodiments described herein, thewidth W may range from approximately 30 μm to approximately 80 μm.

A single circular shape for the wafer seal ring 110 is shown in FIG. 1for illustrative purposes only. In other embodiments, the wafer sealring 110 may comprise a plurality of circular shapes, such as aplurality of concentric circular shaped rings successively surroundingthe dies 120 formed between the dies 120 and the exterior edge of thewafer 100.

The wafer seal ring 110 may be of any suitable shape. For example, FIG.2 illustrates a plan view of a wafer 200 having a wafer seal ring 210according to another embodiment. As illustrated in FIG. 2, the wafer 200may include one or more dies 220 wherein a die seal ring 222 around eachof the one or more dies 220. Each of the dies 220 may be electricallycoupled to one or more conductive test pads 224 that may provideelectrical connections to test and/or verify functionality of electricaldevices (not shown) that may be formed in the dies 220.

In the embodiment as shown in FIG. 2, the wafer seal ring 210 may beformed in manner that may outline a perimeter surrounding a plurality ofdies 220 using a plurality of adjoined segments, such as, for example,straight-line segments. The wafer seal ring 210 may be formed betweenthe plurality of dies 220 and an exterior edge of the wafer 200. Thewafer seal ring 210 may have an approximately uniform width W. The widthW of the wafer seal ring 210 may be sized based on area of the wafer 200not occupied by the dies 220, design guidelines and/or limitations ofthe equipment used to form the wafer seal ring 210. In an illustrativeexample that is not meant to limit the embodiments described herein, thewidth W may range from approximately 30 μm to approximately 80 μm.

A single wafer seal ring 210 is shown in FIG. 2 for illustrativepurposes only. In other embodiments, the wafer seal ring 210 maycomprise a plurality of rings (not shown), which may be polygonal orcircular surrounding the plurality of dies 220. It should be noted thata plurality of rings may be used of various shapes. For example, a wafermay have a polygonal ring inside a circular ring and the like. The shapeof the wafer seal rings shown in FIGS. 1 and 2 are provided forillustrative purposes only and are not intended to implicate limitationstherein. Other embodiments may utilize other shapes.

In various embodiments, the wafer 100 (FIG. 1) and/or the wafer 200(FIG. 2) may be an interposer, a device wafer, a wafer having MEMSdevices formed therein, a handle wafer or the like. In variousembodiments, the wafer seal rings 110, 210 may be made of materials thatmay provide for bonding to another wafer (not shown) using a eutectic ora fusion bonding process. In various embodiments, the wafer seal rings110, 210 may include of a plurality of concentric shaped structures (notshown) formed around the plurality of dies 120, 220 between theplurality of dies 120, 220 and the corresponding edges of the respectivewafers 100, 200.

FIGS. 3A-3C illustrate cross-sectional views of intermediate stages offorming wafer seal ring in accordance with an embodiment. Referringfirst to FIG. 3A, a first wafer 310 may include a first substrate 311having first electrical device layers 313, and/or one more firstinterconnects 312. The composition, connections and layers as describedfor the first wafer 310 are provided for illustrative purposes only arenot intended to implicate specific limitations of the first wafer 310.Only a portion of the first wafer 310 is shown in FIGS. 3A and 3C.

A first die seal ring 315 may be formed on the first wafer 310. A firstwafer seal ring 317 may be formed on the first wafer 310. The firstwafer seal ring 317, as shown in FIG. 3A shows two seal rings forillustrative purposes only. In various embodiments, more or fewer waferseal rings may be formed on the first wafer 310. One or more test pads316 may be formed on the first wafer, which may be coupled to electricaldevices (not shown) formed within the first wafer 310.

The first wafer seal ring(s) 317, as shown in FIG. 3A, may be formed ina manner that may provide for wafer bonding using eutectic bondingprocesses. In such embodiments, the first wafer seal ring(s) 317 and/orthe first die seal 315 may be made of one or more metal layersincluding, but not limited to, a eutectic alloy such as AlCu, AlGe or alow-melting point metal layer such as In, Au, Sn, Cu or other likematerial. The first wafer seal ring(s) 317 may be formed to a heightH_(1SR) and an approximately uniform width W_(1SR). The first die sealring 315 may be formed to a height H_(1DS) and a width W_(1DS).

The height H_(1SR) of the first wafer seal ring(s) 317 may be formed tobe approximately equal to the height H_(1DS) of the first die seal ring315. The width W_(1SR) of the first wafer seal ring(s) 317 may be formedto a width as determined by a designer, design guidelines and/orlimitations of equipment forming the first wafer seal ring(s) 317. Forexample, the width W_(1SR) may be related to an available area of thefirst wafer 310 wherein the first wafer seal ring(s) 317 may be formed.Although the width W_(1SR) may be approximately uniform for each firstwafer seal ring 317, in various embodiments, the individual uniformwidth of each ring may differ from or be approximately equal to thewidth of another wafer seal ring on the first wafer 310. In anillustrative example that is not meant to limit the embodimentsdescribed herein, the width W_(1SR) of the first wafer seal ring(s) 317may range from approximately 30 μm to approximately 80 μm.

In various embodiments, the first electrical device layers 313 mayinclude metal layers, dielectric layers or semiconductor materiallayers. For metal layers, copper, aluminum, gold or other like materialsmay be used in the first electrical device layers 313. For dielectriclayers, one or more dielectric materials such as oxide, nitride, siliconoxide, silicon nitride, low-k dielectrics such as carbon doped oxides,extremely low-k dielectrics such as porous carbon doped silicon dioxide,a polymer such as polyimide, or a combination thereof may be used in thefirst electrical device layers 313. For semiconductor material layers,silicon, quartz, ceramic, silicon-on-insulator (“SOI”), gradient, hybridorientation materials or other materials may be used in the firstelectrical device layers 313.

In various embodiments, the first electrical device layers 313 may alsoinclude active and/or passive electrical devices (not shown) such astransistors, capacitors, resistors, combinations of these and the likeformed therein. In various embodiments, the first electrical devicelayers 313 may also include a cavity 313 a wherein MEMS electricaldevices (not shown) may be formed in an area between first die seal ring315. For example, the MEMS electrical devices may be a vibrating mass,elastic strings or coils for performing functions in sensors,gyroscopes, accelerometers, RF wafers or optical wafers. In anillustrative example, as shown in FIGS. 3A and 3C, the first wafer 310may include the open cavity 313 a wherein MEMS electrical devices (notshown) may be formed. The MEMS electrical devices may include movableelements (not shown) within the cavity.

In an embodiment, the first interconnects 312 may be formed, independentof each other, of copper, aluminum, gold or other like materials toprovide conductive paths between electrical devices formed in the firstelectrical device layers 313. The first interconnects 312 may be formedthrough a process such as, for example, CVD, PVD, electrochemicalplating, one or more subtractive etch processes, single Damascenetechniques, and/or dual-Damascene techniques, the like or otheracceptable methods. In various embodiments, the first electrical devicelayers 313, and/or the first interconnects 312 may be used to formre-distribution layers (“RDLs”) (not shown) within the first wafer 310.The RDLs may be formed using an appropriate process, such as thosediscussed above

In various embodiments, the test pads 316 may be formed of one or moremetal layers including, but not limited to, a eutectic alloy such asAlCu, AlGe or the like or a low-melting point metal layer such as In,Au, Sn, Cu or other like material. In an embodiment, the first substrate311 may comprise bulk silicon. In other embodiments, first substrate 311may comprise any semiconductor substrate, ceramic substrate, quartzsubstrate or the like. Other substrates that may be used includemulti-layered substrates, gradient substrates, or hybrid orientationsubstrates.

As shown in FIG. 3B, a second wafer 320 may be provided. Only a portionof the second wafer 320 is illustrated in FIG. 3B. The second wafer 320may include a second substrate 321. The second wafer 320 may alsoinclude second electrical device layers and second interconnects (allnot shown).

The second wafer 320 may have formed thereon a second die seal ring 325.The second wafer 320 may also have formed thereon a second wafer sealring 327. The second wafer seal ring 327, as shown in FIG. 3B shows twoseal rings on the second wafer 320 for illustrative purposes only. Invarious embodiments, more or fewer wafer seal rings may be formed on thesecond wafer 320. Only a portion of the second wafer 320 is shown inFIGS. 3B and 3C.

The second wafer seal ring(s) 327, as shown in FIG. 3B, may be formed ina manner that may provide for wafer bonding process using eutecticbonding processes. In such embodiments, the second wafer seal ring(s)327 and/or the second die seal ring may be made of one or more metallayers including, but not limited to, a eutectic alloy such as AlCu,AlGe or a low-melting point metal layer such as In, Au, Sn, Cu or otherlike material. The second wafer seal ring(s) 327 may be formed to aheight H_(2SR) and an approximately uniform width W_(2SR). The seconddie seal ring 325 may be formed to a height H_(2DS) and a width W_(2DS).

The height H_(2SR) of the second wafer seal ring(s) 327 may be formed tobe approximately equal to the height H_(2DS) of the second die seal ring325. The second wafer seal ring(s) 327 may be formed to align and havean approximately equal width W_(2SR) with the corresponding first waferseal ring(s) 317, which may promote bonding and sealing for the firstand second wafer seal rings 317, 327. In various embodiments, the heightH_(1SR) of the first seal ring 317, the height H_(1DS) of the first dieseal ring 315, the height H_(2SR) of the second seal ring 327 and/or theheight H_(2DS) of the second die seal ring 325 may be formed to heightsranging from approximately 5000 Å to approximately 20,000 Å.

In an embodiment, the second wafer 320 may be formed as a handle-typewafer, without electrical devices being formed therein. In anembodiment, the second wafer 320 may be formed with passive, activeand/or MEMS electrical devices formed therein. The inclusion orexclusion of electrical devices, connections and/or layers is notintended to implicate specific limitations of the second wafer 320.

Given the partial, cross-sectional views of the first and second wafers310, 320 as shown in FIGS. 3A-3B, an overall shape of the first andsecond wafer seal rings 317, 327 is not fully illustrated. It should beunderstood, however, that the first and second wafer seal rings 317, 327may be formed in a manner to surround the corresponding first and seconddie seal rings 315, 325 between the die seal rings 315, 325 and anexterior edge of the respective first and second wafers 310, 320. Theshape of the first and second wafer seal rings 317, 327 may vary asdescribed for the various embodiments discussed herein.

As illustrated in FIG. 3C, the first wafer 310 and the second wafer 320may be aligned and bonded together to form a bonded structure 330. Forthe bonded structure 330, the first wafer seal ring 317 of the firstwafer 310 may be bonded to corresponding second wafer seal ring 327 ofthe second wafer 320 to form a seal ring structure 340. The first dieseal ring 315 of the first wafer 310 may be bonded to correspondingsecond die seal ring 325 of the second wafer 320 to form a die seal ringstructure 350.

The first and second wafers 310, 320 as shown in FIG. 3C may, forexample, be aligned and bonded using a eutectic bonding process. Invarious embodiments, a pressure and/or a heat may be applied to thefirst wafer 310 and/or second wafer 320 to form the bonded structure330. In an embodiment, for example, a heat may be applied to atemperature in a range from about 100° C. to about 500° C. In anembodiment, for example, a pressure may be in a range from about 10 KNto about 100 KN. For example, for an Al—Ge bonding process, thetemperature may range from approximately 420° C. to approximately 450°C. and the pressure may range from about 30 KN to approximately 55 KN.

Following the eutectic bonding process, the seal ring structure 340 mayprovide a hermetic seal between the first and second wafers 310, 320that may protect the test pads 316, the first die seal ring 315 and/orthe second die seal ring 325 during subsequent post-bonding processingthat may be performed on the bonded structure 330. For example, the sealring structure 340 may provide protection for moisture, chemicals,and/or residue from penetrating the bonded structure 330 duringsubsequent manufacturing processes. For example, such processes mayinclude, but are not limited to, chemical-mechanical polishing (“CMP”),grinding, etching, deposition or other manufacturing processes.

FIGS. 4A-4B illustrate cross-sectional views of intermediate stages forforming a wafer seal ring according to an embodiment. The embodiments asshown in FIGS. 4A-4B may provide for wafer bonding using eutecticbonding processes. FIGS. 4A-4B illustrate a first and a second wafer410, 420. Only a portion of the first and the second wafers 410, 420 isshown in FIGS. 4A-4B.

The first wafer 410 may have formed thereon a wafer seal ring 414comprising a first structural portion 414 a and a second structuralportion 414 b. The first wafer 410 may include a first substrate 411. Onthe first substrate 411, may be formed the first structural portion 414a of the wafer seal ring 414. On the first structural portion 414 a maybe formed the second structural portion 414 b, which may, for example,be a bonding layer for the wafer seal ring 414.

A die seal ring (not shown) may be formed on the first wafer 410. Thewafer seal ring 414 may be formed to an overall height H_(SR) that maybe approximately equal to a height of the die seal ring (not shown). Thewafer seal ring 414 may be formed to have an approximately uniform widthW_(SR). In an embodiment, additional wafer seal rings (not shown) may beformed on the first wafer 410.

The second wafer 420 may include a second substrate 421. The secondwafer 420, as shown in FIG. 4A, may not have a wafer seal ring formedthereon. The first wafer 410 and the second wafer 420 may be aligned andbonded together as shown in FIG. 4B to form a bonded structure 440. Thebonding may be performed using various eutectic bonding processes.Bonding the first and the second wafers 410, 420 together to form thebonded structure 440 may form a seal ring structure 430 between thewafers.

In various embodiments, the first structural portion 414 a of the waferseal ring 414 may be made of a dielectric material, a metal material, ora semiconductor material. In various embodiments, the second structuralportion 414 b of the wafer seal ring 414 may be made of materialsincluding a eutectic alloy such as AlCu, AlGe or the like or alow-melting point metal layer such as In, Au, Sn, Cu or the like. In anembodiment, the second structural portion 414 b may include multiplelayers.

In various embodiments, the first and/or second substrate 411, 421 maycomprise bulk silicon. In other embodiments, first and/or secondsubstrate 411, 421 may comprise any semiconductor substrate, ceramicsubstrate, quartz substrate or the like. Other substrates that may beused include multi-layered substrates, gradient substrates, or hybridorientation substrates.

FIGS. 4C-4D illustrate cross-sectional views of intermediate stages forforming a wafer seal ring according to another embodiment. Theembodiments as shown in FIGS. 4C-4D may provide for wafer bonding usingeutectic bonding processes. FIGS. 4C-4D illustrate a first and a secondwafer 450, 460. Only a portion of the first and the second wafers 450,460 is shown in FIGS. 4C-4D.

The first wafer 450 may have formed thereon a first wafer seal ring 454having a first structural portion 454 a and a second structural portion454 b. The first wafer 450 may include a first substrate 451. On thefirst substrate 451 may be formed the first structural portion 454 a ofthe first wafer seal ring 454. On the first structural portion 454 a maybe formed the second structural portion 454 b, which may, for example,be a bonding layer for the first wafer seal ring 454.

One or more first die seal rings (not shown) may be formed on the firstwafer 450. The first wafer seal ring 454 may be formed to an overallheight H_(1SR) that may be approximately equal to a height of the one ormore first die seal rings (not shown). The first wafer seal ring 454 maybe formed to have an approximately uniform width W_(1SR). In anembodiment, additional first wafer seal rings (not shown) may be formedon the first wafer 450.

The second wafer 460 may have formed thereon a second wafer seal ring464 having a first structural portion 464 a and a second structuralportion 464 b. The second wafer 460 may include a second substrate 461.On the second substrate 461, may be formed the first structural portion464 a of the second wafer seal ring 464. On the first structural portion464 a may be formed the second structural portion 464 b, which may, forexample, be a bonding layer for the second wafer seal ring 464.

One or more second die seal ring (not shown) may be formed on the secondwafer 460. The second wafer seal ring 464 may be formed to an overallheight H_(2SR) that may be approximately equal to a height of the one ormore second die seal rings (not shown). The second wafer seal ring 464may be formed to have an approximately uniform width W_(2SR). The secondwafer seal ring 464 may be formed to align and have an approximatelyequal width W_(2SR) with the first wafer seal ring 317, which maypromote bonding and sealing for the first and second wafer seal rings317, 327. In an embodiment, additional second wafer seal rings (notshown) may be formed on the second wafer 460.

The first wafer 450 and the second wafer 460 may be aligned and bondedtogether as shown in FIG. 4D to form a bonded structure 480. The bondingmay be performed using various eutectic bonding processes. Bonding thefirst and the second wafers 450, 460 together may include bonding thefirst and second wafer seal rings 454, 464 together, which may form aseal ring structure 470 between the first and the second wafers 450,460.

In various embodiments, the first structural portion 454 a of the firstwafer seal ring 454 may be made of a dielectric material, a metalmaterial, or a semiconductor material. In various embodiments, thesecond structural portion 454 b of the first wafer seal ring 454 may bemade of materials including, but not limited to, a eutectic alloy suchas AlCu, AlGe or the like or a low-melting point metal layer such as In,Au, Sn, Cu or the like. In an embodiment, the second structural portion454 b may include multiple layers.

In various embodiments, the first structural portion 464 a of the secondwafer seal ring 464 may be made of a dielectric material, a metalmaterial, or a semiconductor material. In various embodiments, thesecond structural portion 464 b of the second wafer seal ring 464 may bemade of materials including, but not limited to, a eutectic alloy suchas AlCu, AlGe or the like or a low-melting point metal layer such as In,Au, Sn, Cu or the like. In an embodiment, the second structural portion464 b of the second wafer seal ring 464 may include multiple layers.

In various embodiments, the first and/or second substrate 451, 461 maycomprise bulk silicon. In other embodiments, first substrate and/orsecond substrate 451, 461 may comprise any semiconductor substrate,ceramic substrate, quartz substrate or the like. Other substrates thatmay be used include multi-layered substrates, gradient substrates, orhybrid orientation substrates.

FIGS. 5A-5B illustrate cross-sectional views of intermediate stages forforming a wafer seal ring according to an embodiment. The embodiments asshown in FIGS. 5A-5B may provide for wafer bonding using fusion bondingprocesses. FIGS. 5A-5B illustrate a first and a second wafer 510, 520.Only a portion of the first and second wafers 510, 520 is shown in FIGS.5A-5B. The first wafer 510 may have formed thereon a wafer seal ring514. The wafer seal ring 514 as shown in FIGS. 5A-5B illustrate two sealrings. In various embodiments, more or fewer wafer seal rings may beformed on the first wafer 510.

The first wafer 510 may include a first substrate 511. One or more dieseal rings (not shown) may be formed on the first wafer 510. The waferseal ring(s) 514 may be formed to a height H_(SR) that may beapproximately equal to a height of the one or more die seal rings (notshown). The wafer seal ring(s) 514 may be formed to have anapproximately uniform width W_(SR). Although the width W_(SR) may beapproximately uniform for each wafer seal ring 514, in variousembodiments, the individual uniform width of each ring may differ fromor be approximately equal to the width of another ring on the firstwafer 510.

The second wafer 520 may include a second substrate 521. The secondwafer 520 may not have a wafer seal ring formed thereon. The first wafer510 and the second wafer 520 may be aligned and bonded together as shownin FIG. 5B to form a bonded structure 540. The bonding may be performedusing various fusion bonding processes. In various embodiments, apost-bond anneal may be performed may be performed at temperaturesranging from approximately 300° C. to approximately 1000° C., which mayenhance bonding strength. Bonding the first and second wafers 510, 520together to form the bonded structure 540 may form a seal ring structure530 between the first and second wafers 510, 520.

In various embodiments, the first and/or second substrate 511, 521 maycomprise bulk silicon. In other embodiments, first substrate and/orsecond substrate 511, 521 may comprise any semiconductor substrate,ceramic substrate, quartz substrate or the like. Other substrates thatmay be used include multi-layered substrates, gradient substrates, orhybrid orientation substrates.

In various embodiments, the wafer seal ring 514 may be made of asemiconductor material or a substrate material which may be the same asor different from the materials of the first and/or second substrate511, 521. In various embodiments, the wafer seal ring 514 may be formedon the second wafer 520 rather than the first wafer 510, as determinedby a designer.

FIGS. 5C-5D illustrate cross-sectional views of intermediate stages forforming a wafer seal ring according to another embodiment. Theembodiments as shown in FIGS. 5C-5D may provide for wafer bonding usingfusion bonding processes. FIGS. 5C-5D illustrate a first and a secondwafer 550, 560. Only a portion of the first and second wafers 550, 560are shown in FIGS. 5C-5D.

The first wafer 550 may include a first substrate 551. The first wafer550 may have formed thereon a wafer seal ring 554. The wafer seal ring554 as shown in FIGS. 5A-5B illustrate two seal rings. In variousembodiments, more or fewer wafer seal rings may be formed on the firstwafer 550. One or more die seal rings (not shown) may be formed on thefirst wafer 550. The wafer seal ring(s) 554 may be formed to a heightH_(SR) that may be approximately equal to a height of the one or moredie seal rings (not shown).

The wafer seal ring(s) 554 may be formed to have an approximatelyuniform width W_(SR). Although the width W_(SR) may be approximatelyuniform for each wafer seal ring 514, in various embodiments, theindividual uniform width of each ring may differ from or beapproximately equal to the width of another ring on the first wafer 510.

The second wafer 560 may include a second substrate 561 and an alignmentpost 562. The alignment post 562 may aid in alignment of the first andsecond wafer 550, 560 during wafer bonding. The alignment post 562 maybe formed to a height Hp, which may be approximately equal to or lessthan the height H_(SR) of the wafer seal ring(s) 554. The alignment post562 may be formed at a location on the second wafer 560 that may promotealignment with the first wafer 550. For example, the alignment post 562,as shown in FIG. 5C may be formed on the second wafer 560 to alignbetween the wafer seal ring(s) 554 for bonding the first and secondwafers 550, 560.

In various embodiments, a plurality of alignment posts (not shown) maybe formed to align on opposing sides of the wafer seal ring(s) 554. Itshould be understood, that use of an alignment post is not limited toembodiments incorporating fusion bonding processes and may also be usedin embodiments incorporating eutectic bonding processes as discussedpreviously.

The first wafer 550 and the second wafer 560 may be aligned and bondedtogether as shown in FIG. 5D to form a bonded structure 580. The bondingmay be performed using various fusion bonding processes. Bonding thefirst and second wafers 550, 560 together to form the bonded structure580 may form a seal ring structure 570 between the first and secondwafers 550, 560.

In various embodiments, the first and/or second substrate 551, 561 maycomprise bulk silicon. In other embodiments, first substrate and/orsecond substrate 551, 561 may comprise any semiconductor substrate,ceramic substrate, quartz substrate or the like. Other substrates thatmay be used include multi-layered substrates, gradient substrates, orhybrid orientation substrates. In various embodiments, the wafer sealring 554 may be made of a semiconductor material or a substrate materialwhich may be the same as or different from the materials of the firstand/or second substrate 551, 561.

In an embodiment, an apparatus is provided. The apparatus may include apair of bonded wafers, at least one of the wafers having a pluralitydies formed thereon; a plurality of die seal rings, wherein each of thedie seal rings is formed around each of the plurality of dies; and awafer seal ring between the bonded wafers, the wafer seal ring having auniform width, wherein the wafer seal ring is formed to surround theplurality of die seal rings The wafer seal ring may be formed to aheight approximately equal to a height of the die seal rings.

In another embodiment, another apparatus is provided. The apparatus maya wafer having a plurality of dies formed thereon; a plurality of dieseal rings, each die seal ring formed around each of the plurality ofdies; and a wafer seal ring, the wafer seal ring having a uniform width,wherein the wafer seal ring is formed to surround the plurality of dies.The wafer seal ring may be formed to a height approximately equal to aheight of the die seal rings.

In another embodiment, a method is provided. The method may compriseforming a plurality of dies on a wafer; forming a plurality of die sealrings on the wafer, each die seal ring formed around a correspondingdie; and forming a wafer seal ring on the wafer, wherein the wafer sealring surrounds the plurality of dies and is formed to a heightapproximately equal to a height of the plurality of die seal rings.

In another embodiment, a method includes forming a plurality of dies ona first wafer. A plurality of die seal rings is formed on the firstwafer, each die seal ring encircling a corresponding die of theplurality of dies. A first wafer seal ring and a second wafer seal ringare formed on the first wafer, wherein the first wafer seal ringsurrounds the plurality of dies, and wherein the second wafer seal ringsurrounds the first wafer seal ring. An alignment post is formed on asecond wafer. The first wafer is aligned with respect to the secondwafer by inserting the alignment post in a gap between the first waferseal ring and the second wafer seal ring. The first wafer is bonded tothe second wafer to form a bonded structure.

In another embodiment, a method includes forming a plurality of dies ona first wafer. A plurality of die seal rings is formed on the firstwafer, each die seal ring encircling a corresponding die of theplurality of dies. A first layer of a plurality of concentric wafer sealrings is formed on the first wafer, the first layer of the plurality ofconcentric wafer seal rings comprising a first material. A second layerof the plurality of concentric wafer seal rings is formed on the firstlayer of the plurality of concentric wafer seal rings, the second layerof the plurality of concentric wafer seal rings comprising a secondmaterial, the plurality of concentric wafer seal rings encircling theplurality of die seal rings. The first wafer is bonded to a secondwafer.

In another embodiment, a structure includes a first wafer, the firstwafer including a die, and a die seal ring on the first wafer, the dieseal ring encircling the die, the die seal ring having a first height.The structure further includes a first wafer seal ring on the firstwafer, the first wafer seal ring surrounding the die seal ring, thefirst wafer seal ring having a second height, the first height beingsubstantially equal to the second height, and a second wafer seal ringon the first wafer, the second wafer seal ring encircling the firstwafer seal ring, the second wafer seal ring having the second height.The structure further includes a second wafer bonded to the first wafer,and an alignment post on a second wafer, the alignment post beinginterposed between the first wafer seal ring and the second wafer sealring.

Although the present embodiments and their advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the disclosure as defined by the appendedclaims. For example, it will be readily understood by those skilled inthe art that the structures and ordering of steps as described above maybe varied while remaining within the scope of the present disclosure.For example, formation of wafer seal rings on either wafer is within thescope of the present disclosure.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method comprising: forming a plurality of dieson a first wafer; forming a plurality of die seal rings on the firstwafer, each die seal ring encircling a corresponding die of theplurality of dies; forming a first wafer seal ring and a second waferseal ring on the first wafer, wherein the first wafer seal ringsurrounds the plurality of dies, and wherein the second wafer seal ringsurrounds the first wafer seal ring; forming an alignment post on asecond wafer; aligning the first wafer with respect to the second waferby inserting the alignment post in a gap between the first wafer sealring and the second wafer seal ring; and bonding the first wafer to thesecond wafer to form a bonded structure.
 2. The method of claim 1,further comprising forming a MEMS device on at least one of the firstwafer and the second wafer.
 3. The method of claim 1, wherein bondingthe first wafer to the second wafer comprises using a fusion bondingmethod.
 4. The method of claim 1, wherein bonding the first wafer to thesecond wafer comprises using an eutectic bonding method.
 5. The methodof claim 1, forming the first wafer seal ring comprises: forming a firstlayer of the first wafer seal ring on the first wafer; and forming asecond layer of the first wafer seal ring on the first layer of thefirst wafer seal ring.
 6. The method of claim 1, wherein a height of thealignment post is less than a height of the first wafer seal ring. 7.The method of claim 1, wherein a width of the alignment post issubstantially equal to a width of the gap.
 8. The method of claim 1,further comprising annealing the bonded structure.
 9. A methodcomprising: forming a plurality of dies on a first wafer; forming aplurality of die seal rings on the first wafer, each die seal ringencircling a corresponding die of the plurality of dies; forming a firstlayer of a plurality of concentric wafer seal rings on the first wafer,the first layer of the plurality of concentric wafer seal ringscomprising a first material; forming a second layer of the plurality ofconcentric wafer seal rings on the first layer of the plurality ofconcentric wafer seal rings, the second layer of the plurality ofconcentric wafer seal rings comprising a second material, the pluralityof concentric wafer seal rings encircling the plurality of die sealrings; and bonding the first wafer to a second wafer.
 10. The method ofclaim 9, further comprising: before bonding the first wafer to thesecond wafer, forming an alignment post on the second wafer; andaligning the first wafer with respect to the second wafer by insertingthe alignment post between adjacent wafer seal rings of the plurality ofconcentric wafer seal rings.
 11. The method of claim 10, wherein a widthof the alignment post is substantially equal to a width of a distancebetween the adjacent wafer seal rings of the plurality of concentricwafer seal rings.
 12. The method of claim 9, wherein the first materialis a dielectric material and the second material is an eutecticmaterial.
 13. The method of claim 9, wherein the first material is asemiconductor material and the second material is an eutectic material.14. The method of claim 9, wherein the first material is a metallicmaterial and the second material is an eutectic material.
 15. The methodof claim 9, wherein a height of the plurality of die seal rings issubstantially equal to a height of the plurality of concentric waferseal rings.
 16. A structure comprising: a first wafer, the first wafercomprising a die; a die seal ring on the first wafer, the die seal ringencircling the die, the die seal ring having a first height; a firstwafer seal ring on the first wafer, the first wafer seal ringsurrounding the die seal ring, the first wafer seal ring having a secondheight, the first height being substantially equal to the second height;a second wafer seal ring on the first wafer, the second wafer seal ringencircling the first wafer seal ring, the second wafer seal ring havingthe second height; a second wafer bonded to the first wafer; and analignment post on a second wafer, the alignment post being interposedbetween the first wafer seal ring and the second wafer seal ring. 17.The structure of claim 16, wherein at least one of the first wafer andthe second wafer comprises a MEMS device.
 18. The structure of claim 16,wherein a width of the alignment post is substantially equal to adistance between the first wafer seal ring and the second wafer sealring.
 19. The structure of claim 16, further comprising a test padelectrically coupled to the die, the die seal ring being interposedbetween the test pad and the die.
 20. The structure of claim 16, whereinthe first wafer seal ring comprises: a first layer comprising a firstmaterial; and a second layer on the first layer, the second layercomprising a second material.